Desmodu Bat, Guard (CR 3)

Large Animal
Alignment: Always neutral
Initiative: +6 (Dex); Senses: blindsense 120 ft., Listen +12*, and Spot +12*

AC: 20 (-1 size, +6 Dex, +5 natural), touch 15, flat-footed 14
Hit Dice: 4d8+12 (30 hp)
Fort +7, Ref +10, Will +6
Speed: 20 ft., fly 60 ft. (good)
Space: 10 ft./5 ft.
Base Attack +3; Grapple +10
Attack: Bite +5 melee
Full Attack: Bite +5 melee
Damage: Bite 1d8+4 plus wounding
Special Attacks/Actions: Wounding
Abilities: Str 17, Dex 22, Con 17, Int 2, Wis 14, Cha 7
Special Qualities: immunities
Feats: Dodge; Mobility; Spring Attack
Skills: Listen +12*, Move Silently +9, and Spot +12*
Advancement: 5-12 HD (Huge)
Climate/Terrain: Underground
Organization: Solitary or colony (5-8)
Treasure/Possessions: None

Source: Monster Manual II

Wounding (Ex): A guard bat's saliva contains an anti-coagulant that causes bite wounds the creature inflicts to bleed freely. A wound resulting from a guard bat's bite attack bleeds for an additional 1 point of damage per round thereafter. Multiple wounds from such attacks result in cumulative bleeding loss (two wounds for 2 points of damage pet round, and so on). The bleeding can be stopped only by a successful Heal check (DC 15) or the application of a cure spell or some other healing spell (heal, healing circle, or the like).

Blindsight (Ex): A bat emits high-frequency sounds, inaudible to most other creatures, that bounce off nearby objects and creatures. This ability enables it to discern objects and creatures within 120 feet. The bat usually does not need to make Spot or Listen checks to notice creatures within range of its blindsight. A silence spell negates this ability and forces the bat to rely on its weak vision, which has a range of 10 feet.

Immunities: The bats the desmodus breed are immune to the despair and stunning screech abilities of desmodus.

Skills: A guard bat receives a +8 racial bonus on Spot and Listen checks. These bonuses are lost if blindsight is negated.

Like other bats, these creatures fight on the wing, swooping down to bite their foes.

In battle, a group of guard bats typically picks out a single target and swoops in to bite. Then each guard bat uses its Spring Attack feat to bite and fly out of reach before the foe can respond.